sensation and perception sensory input and psychophysics
TRANSCRIPT
Sensation and Perception
Sensory input and Psychophysics
Sensation and Perception
What do you hear? What do you see? What do you taste? What do you smell? What do you feel? (not emotion) What conclusions can you draw from
these answers?
Sensation
Starts with a stimulus (any aspect of change in our environment to which we respond)
Can be measured in size, duration, intensity and wavelength
Occurs anytime a stimulus activates a receptor
Sensory Receptor
Living cell that responds to certain type of energy
Often located in sense organsSpecialized structure that collects
energy particularly well… (eye, ear, etc)
Detect physical changes in energy such as heat, light, sound, and physical pressure
Eye- notes changes in light
Ear- notes changes in sound
Skin- notes changes in heat and pressure
Perception
Organization of sensory information into a meaningful experience
Comes from a combination of sensations and past experiences Translating the stimulus into the language of
the nervous system (neural impulse) comprehending the basic components of
the stimulus, size, shape, color Organizing the components into an
understandable explanation
Psychophysics
The interaction between the physical world (stimuli) and the psychological world (internal experience)
What is the relationship between color and wavelength?
How does changing a light’s intensity affect your perception of it’s brightness?
Threshold
How much energy is required for someone to hear a sound, or see a light?
How much of a scent must be in a room for someone to smell it?
How much pressure must be put on the skin for someone to feel it?
Is it the same for everyone?
How strong must a stimulus be in order for detection? Threshold- dividing line Not exact Absolute threshold- point at which a very
weak stimulus can be detected 50% of the time
Difference threshold- smallest change a person can detect 50% of the time.
(JND) just noticeable difference
Absolute threshold for 5 senses
Vision- seeing a candle flame 30 miles away on a clear night
Absolute threshold
Hearing- watch ticking 20 feet away
Absolute Threshold
Tasting- 1 teaspoon of sugar dissolved in 2 gallons of water
Absolute threshold
Smell- 1 drop of perfume in a 3 room house
Absolute threshold
Touch- feeling a bee’s wings falling a distance of 1 centimeter onto your cheek
Weber’s Law- related to the Just Noticeable Difference (also known as the difference threshold), which is the minimum difference in stimulation that a person can detect 50 percent of the
time.
The larger the magnitude of the stimulus, the larger the JND
25 watt light bulb / 50 watt light bulb very different
175 watt light bulb / 200 watt light bulb hard to notice
Weber’s Law
The JND increases in direct proportion to the intensity of the stimulus.
Often not true when stimuli approach extreme values.
Sensory adaptation
Our senses are tuned to change and respond to increases and decreases in stimuli, or new events rather than constant stimulation.
We adapt to change/deviation in stimulation
Movie theater Clothes on body
Signal Detection theory- how good are you at recognizing stimuli?
Study of people’s tendencies to make correct judgments in detecting the presence of stimuli
Recognizing stimuli against a competing background of stimuli
Individuals vary based on situation Radar operator
Signal Detection theory
Pre-attentive process- getting info automatically and simultaneously when presented with stimuli
Attentive process- paying attention to only one of the stimuli at a time when presented with multiple stimuli
All tasks require attention, but some require more than others.
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